Fluid flow control valves are known in which a valve plunger is slidable within a valve hosing, under the control of a rotatable control cam, to compress a deformable tube extending through the housing and which in use passes a flow of fluid. In the prior art, it is known to provide a rotatable cam having a camming surface which is oblique to the axis of rotation of the cam. It is also known to provide the cam with a circumferential surface of varying radius about the axis of rotation. The intention of the differing proposals is to provide better control over the deformation of the tube which provides the valving action. However, the achievement of an efficient valving action still presents problems and it is an object of this invention to provide a construction of fluid flow control valve in which an improved valving action is obtained.